2eighTZ4me Posted June 15, 2012 Share Posted June 15, 2012 Beautiful morning at Road Atlanta today!!! Turned into a crappy morning quickly... last PDX in March(to make a long story short) started losing oil pressure about 6 laps in. I found it to be a clogged screen element (Oberg 2 stage sandwich filter - the fine screen this time) - plugged up with this 'black carbon' looking schmootz. Cleaned it out - fired it up - voila - pressure. Today - however (once again - 6 laps - doggin' and floggin' - 17psi pulls) - oil temp drops from 250 to naught - pressure goes to hell in a handbag. Open 'er up and....yowza!!! There's half my bearings all chipped up ready to serve....on the coarse screen. I put 100 miles on the car yesterday and beat it as hard as I could on the street (without upsetting the constabularies) - cleaned the filter last night - nothing - clean as a whistle. Today, however, let's see - 6 x 2.54 miles = 15.24 miles - my bearings are toast. Any ideas why I may be chewing up bearings? Under severe boost only? SUSTAINED boost. Running Mobil 1 synthetic 10w30 (after breaking in the motor with Valvoline for 400 miles) - I do not put my foot on the clutch when I start the car - such as wear on the thrust bearing The tune is dead nvts - Jerry from DIY AutoTune did it. Spark and fuel. These are Nissan factory bearings - standard size. Stroker crank - block was line bored. Guess I can cry over my doughnuts - but the motor ain' pulling itself (I should still be at the track right now carving laps with it....BUT unfortunately - I'm going now to pull it out) - so I'll post pics later of what I find is coming apart. Quote Link to comment Share on other sites More sharing options...
randy 77zt Posted June 15, 2012 Share Posted June 15, 2012 Oil starvation in the turns?I have ran 13-14 lbs boost all day at thunderhill(3.2 miles per lap) at 100 degress no problem.but I dont believe in the new lower viscosity oil types.I prefer valvoline 20-50 racing.Most motor oil doesnt have moly or zinc in it anymore.Take your time during the teardown/autopsy.IF just the rod bearings are afffected I would be thinking preignition .If all parts are affected it would be oil starvation.even though my car ran on pump gas I always ran 10 gallons of 100 octane race gas + some pump on track days-cheap insurence.the race gas was 100 no lead. Quote Link to comment Share on other sites More sharing options...
letitsnow Posted June 16, 2012 Share Posted June 16, 2012 The 1st thing I thought of was starvation in the corners. It might be wise to setup an oil pressure sensor to datalog. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 16, 2012 Share Posted June 16, 2012 you don't always hear detonation, and it will beat out your bearings bigtime. VW's do that when they run lean at the top end. We would never go more than 25 runs with the high compression motor without checking the bearings. When the Olberg came out it was a godsend! Used it EXACTLY like you are! When you start seeing flecks on the screen, time for a refresh. Fatten it up, look for the other signs of detonation... Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 16, 2012 Author Share Posted June 16, 2012 Well - this is interesting......rod bearings are completely unscathed. They look near brand new. Having difficulty getting the BHJ damper off, so I haven't been able to see the mains. My turbo is munched too. Shaft play out the wazoo. When I drained the oil in the motor, it looked like someone threw a handful of glitter in with the oil. The bottom of the pan was loaded. BTW - this is an AZC baffled oil pan. There is no starvation in the corners. I made sure to watch my pressure several times in the corners - no drop whatsoever. I"m really beginning to wonder if it isn't the turbo that's coming apart......it's a POS Chinese SSC turbo....prolly time for a good ball bearing turbo.....if I can afford it after I clear up this mess!! Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 16, 2012 Share Posted June 16, 2012 You are monitoring your oil pressure through a large-bore hose and mechanical gauge, right? Stick a 5psi Hobbs Pressure Switch in your turbo-oil feed (opens at 5psi) and connect a BIG ORANGE LIGHT (LED is BETTER!) to ground through it (power off ACC relay.) You will be amazed how low your oil pressure gets in turns while most oil pressure gauges merrily show 'just a little drop'... An LED Trailer Light works great, right on the dash. I lunched my turbo at the Auto-X at MSA one year. ... It does happen! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 17, 2012 Author Share Posted June 17, 2012 Yes - pressure is from a -3 AN hose all the way to an AutoMeter mechanical gauge. The pan is 7 quarts - and I don' t (can't is a better term) drive it very hard Anyways - the moment you've been waiting for....... Notice all the nice shiny flakes. When I pulled the pan plug - the oil came out on my hand it it felt like someone had thrown a handful of glitter in for good measure.... Notice the center thrust bearing....it is actually black from what looks like being burned. The other bearings showed signs of the copper metal being embedded into their surface. It must have been a wild ride in that motor with shmootz flying everywhere. The further away from the center bearing though - the less embedded debris was on the other bearings. The ones at either end were almost dead clean. The #5 cap bearing appeared to have shrunk from the heat, as it wouldn't even sit in the cap without falling out. Interestingly enough - it didn't spin because the bearing on the block side was just fine and held in in place. Burn baby burn!!! Note the deformation of the center thrust bearing at the top of the pic. That 'dent' went down about 3mm along the bearing channel. And now - drumroll please..... The crank Yep - that's large pieces of the copper portion of the bearing that was stuck to the crank when I pulled it out. And the poor crank itself. My machinst thinks it will polish out though. So - these are Nissan factory bearings - what I have come to know as good quality - not sure why they would have done this. I was fairly lucky to have made it home. Those bearings were toast!!! Rod bearings were just fine. Nary a fleck of copper metal on them. Machinist is looking into some high quality racing bearings and will be performing an autopsy this week to see if he can determine the cause. I seriously wonder if this had anything to do with a stroker crank flexing under severe load? I know others have done turbo strokers with success. My machinist has been working on these motors for over 30 years and knows what he's doing - he says he's never seen anything like what I did.... We will be balancing the entire rotating assembly this time - from damper to clutch and everything in between. Quote Link to comment Share on other sites More sharing options...
duragg Posted June 18, 2012 Share Posted June 18, 2012 Are the turbo bearings toast too? Maybe the debris from the CCB in the turbo smoked the mains? That crank... hmm. Maybe you should try a stock L28 crank? I think i have one here if you wanna trade... Assuming you reject my generous offer; While re-working your V07 crank is this a good time to do some offset grind-weld-grind work for more stroke? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 18, 2012 Author Share Posted June 18, 2012 Haven't pulled the turbo apart yet - but most everything I found was in the bottom end. The head was clean - no metal anywhere around the cam or springs, none in the front cover area - it seemed to be localized only to the pan and surrounding areas. Appreciate the offer to trade for a stock crank - but I have two of them in the shed gathering dust. Can't really redo any offsetting on the crank either. The pistons are JE custom slugs designed specifically for a stroker crank and 240 rods - they have a custom pin height such that all 3 work as a single unit. Quote Link to comment Share on other sites More sharing options...
B. Whisky Posted June 18, 2012 Share Posted June 18, 2012 What did those piston run you, if you dont mind me asking? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 18, 2012 Author Share Posted June 18, 2012 It's funny you ask - I bought the car from a friend who got it from Eric Chapman (Z-Quip) - 3 years later after I got it running in NA trim - the guy I bought the car from called and said he had a set of pistons for a stroker setup. These were the pistons Eric had custom made some 5 years earlier that somehow resurfaced into my buddy's hands. I gave him $600 for the set. I still have the original box that has the specs and the order # on it. If JE does a good job at archiving records - they should be able to pull the order number and know exactly how to replicate them. Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted June 18, 2012 Share Posted June 18, 2012 What was your oil temperature? Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 19, 2012 Author Share Posted June 19, 2012 (edited) Got to a little less than 250 before the filter started bypassing the temp gauge.Which then, it went to about naught - which is why I knew the filter was clogged. Edited June 19, 2012 by 2eighTZ4me Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted June 24, 2012 Share Posted June 24, 2012 Oil temp of 300 seems to be the magic number where you see bearings in the bottom end suffering. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 24, 2012 Author Share Posted June 24, 2012 OK - haven't had the time to post - spoke with my machinist on Sat. Here's a bit of information you might not find on this site. The stroker crank is .003 narrower on the center journal than a stock L series motor. We suspected the center thrust bearing all along due to the copper shavings, guess I didn't check the end play and 'assumed' it was correct. The crank basically was being squeezed by the main cap. Under normal NA circumstances, this doesn't pose a problem. You put the motor on the track and subject it to extreme pressures and temperatures of turbocharging - it becomes an issue. End play is supposed to be around .006" and I already ate 3 thousandths off that. No room for oil to get into the thrust area. Sooo... he's grinding the crank out to accommodate the extra width. This would explain the burnt center bearing - got hot due to no oil flow. Machinist thought that there was a thrust issue and dug into his reference books and found that the measurements were different. It is something I would like someone to verify before this information becomes BS or good advice. I won't have access to the uncut crank until it's been modified - but I found this very interesting and highly plausible. I have a stock crank to measure - but not a stroker crank that's unmodified. Whoda thunk it??? Thoughts???? Quote Link to comment Share on other sites More sharing options...
duragg Posted June 25, 2012 Share Posted June 25, 2012 Checked a stock engine manual and it says .002" to .007". Do you think you had three-thou? Or no thou? Maybe a hotrod motor needs a little more oil there and more to the high end of spec? Do they make bearings to adjust that? Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 25, 2012 Share Posted June 25, 2012 "guess I didn't check the end play and 'assumed' it was correct." Measure 3X, Assemble Once! I always check and lap the thrust bearings to where they need to be. Picked it up teething on VW Air Cooled Engines where you have to set the end play with shims on the flywheel and you do it on every one! At least you know why now. That is completely within the realm of believable happenings. We continually disassemble machines at my job where we see thrust bearings coked and overheated. Outside of an oiling issue (which normally wrecks the journals first) when we see journals fine and thrust faces all grunged up and damaged--we check the oil clearance an without fail someone skimped on the clearances. Generally ANY bearing requires 0.003" for proper oil flow through the surface. This is big enough to let a continual flow cool the surface, build a proper hydrodynamic wedge, and let small swarfs (like fuel soot in the oil or the odd bit of broken off varnish from the oiling gallery) pass easily through. Go even 0.001" smaller to the 0.002" range and you run the risk of running hot and making varnish (which closes it up further, meaning more heat, meaning more varnish, meaning less clearances and so on and so on and so on...) Going to 0.004" and you decrease oil pressure if you have a marginal pumping system, but watching the oil throwoff temperatures you see it drop by almost 15F! (We can do this for new Engineers to demonstrate what gearbox setup items are critical. We can change these on our machines in about two hours while on the test stand...) On our High Speed Pinions (54K rpm) you will routinely see 75C with 0.003", but 66C at 0.004", and 85-90C at 0.002"!!! This is on the 'active' thrust side... the inactive always runs cooler due to little or no load so we don't instrument it. Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted June 27, 2012 Author Share Posted June 27, 2012 I'm guessing NO thousandths....maybe 1 or 2 - but so thin that oil couldn't make its' way in there to lube and cool the bearing. Won't be making that mistake again. The crank is being cut/widened on the center journal to match a stock L series crank. That way - should I ever have to replace bearings again - I can use stock bearings without having to modify them. Quote Link to comment Share on other sites More sharing options...
Tony D Posted June 27, 2012 Share Posted June 27, 2012 I got news, lapping of the bearings for the clearance you desire is something that happens a lot. Guys open these clearances for a variety of reasons... but understand the only time you really have pressure on it, REAL pressure is when the clutch is depressed. Any other time, the load on it is minimal... The oil wedge shouldn't have an issue at any other time. Chances are you were way tight! If it was on both sides... then definitely that is what it was! Quote Link to comment Share on other sites More sharing options...
2eighTZ4me Posted July 2, 2012 Author Share Posted July 2, 2012 (edited) Well - here's some interesting news. My machinist went back to his reference books and found TWO different diesel cranks. One crank does indeed share the same journal width as the gas powered L series - the other one (which by stroke of luck I happened to get) is .003 thinner on the main thrust journal. Why they did that? My guess - automatic vs. manual transmission is the only thing I can think of. <br><br>Crank has been fixed and widened, however, my machinist is having a bear of a time finding racing bearings for this motor. Apparently, King, Clevite, and others have discontinued racing bearings for this motor as of Q1 this year. Anyone else got a source? Edited July 2, 2012 by 2eighTZ4me Quote Link to comment Share on other sites More sharing options...
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